He founded the Watami chain of izakaya restaurants and headed the company until 2011, when he resigned to run in the 2011 Tokyo gubernatorial election.

Watanabe's run for the governorship of Tokyo was inspired by Michael Bloomberg's mayorship of New York City.

[4] In Japan, Watanabe purchased an educational corporation which had been in financial difficulties due to the advice of Hirofumi Shimomura, a member of the House of Representatives and one of Shinzo Abe's aides.

[11] In addition, at the nursing home operated by Watanabe, due to carelessness of employees caused by their harsh labor, multiple death accidents occurred.

[12] In 2012, Japanese-language magazine Area reported that Watanabe made a female staffer of its educational corporation his mistress, like "a sexual tool", and abandoned her like garbage with only a notification of mobile e-mail.